Low-inertia presserfoot for sewing machines

ABSTRACT

A sewing machine presser mechanism is disclosed having a low inertia presser-foot which is automatically driven through its cooperation with the feed dog in order to effect the feeding of the uppermost ply of superimposed plies being sewn. The low-inertia presser-foot is yieldingly pressed by independent biasing means disposed in a longitudinal recess within the presser bar of the presser mechanism.

U Umted States Patent 1191 1111 3,863,580 Marforio 1 Feb. 4, 1975 [54] LOW-INERTIA PRESSERFOOT FOR 2,344,414 3/1944 Ritter 112/235 SEWING MACHINES 2,616,382 11/1952 Johnson..... 112/235 3,294,047 12/1966 Graham 112/235 Inventor: Nermo Marforw, Mllan, Italy 3,495,560 2/1970 Walling 112/235 3,570,427 3/1971 Wenz et a1 112/212 [73] Asslgnee' 'P' 3,757,714 9/1973 GUStmHnn et a1 112/212 Mllan, Italy [22] Filed: 1973 Primary Examiner-Werner H. Schroeder [21] App1. No.: 343,987

[57] ABSTRACT [30] Forelgn Application Pnomy Data A sewing machine presser mechanism is disclosed hav- Apr. 13, 1972 Italy 23075/72 ing a low inertia pressepfoot Which is automatically driven through its cooperation with the feed dog in [52 U.S. Cl. 112/212, 112/235 Order to effect the feeding of the uppermost ply f 51] Ir |t. (:1 D05b 27/04 perimposed plies being Sewn, [58] Fleld of Search 112/212,213,235, 237

r The low-mertla presser-foot 1s yleldmgly pressed by 159 12321917111 1:314 12:221

UNITED STATES PATENTS mechanism. p p 2,161,141 6/1939 DeVoe 112/235 2,280,193 4/1942 LeVesconte 112/235 5 Claims, 3 Drawing [Figures PATENTED FEB 45175 SHEET 10F 2 PATENTED 4|975 3 863 580 sum 20F 2 LOW-INERTIA PRESSERFOOT FOR SEWING MACHINES BACKGROUND OF THE INVENTION The present invention refers to a low-inertia presserfoot device for sewing machines including a presserfoot having a sole portion with a fulcrum point on an oscillating support, the latter being hinged to the presserfoot bar which is biased downwardly by independent biasing means against the feed dog of the feeding device and therefore against the needle plate.

Presser-feet constructed in the mentioned way are well known and their use has been in great demand to obtain a desired forward movement of the work in view of the difficulty experienced with synthetic fabrics by the making up industry. With the aim of improving the forward movement of the work, the resser-foot has been fitted with independent biasing means which is lighter than the normal fabric pressing spring and functions to assure contact of the sole portion of the presserfoot with the feed dog during the time that it protrudes through the needle plate and to cause it to follow an arcuated path which at the end of its cycle is moving in the same direction of the forward movement of the workpiece and is effective in serving as an upper feeding device that assists in advancing said workpiece.

The independent biasing means is capable of absorbing the thrust exerted by the feed dog when it protrudes from the needle plate and continuously maintains contact of the sole portion of the presser-foot with the feed dog unchanged during the entire portion of the work feeding cycle and for as long as it protrudes from the needle plate.

There must also be provided means to limit the movement of the lifting device of the presser-foot bar from the needle plate, so as to interrupt the action of the normal fabric pressing spring and allow only the independent biasing means to insure desired contact between the presser-foot and the feed dog.

The independent biasing means must be adjustable so that the presser-foot will exert a pressure proportionate to the thickness of the work, not so much in order to increase or diminish it as the thickness of the work changes but to keep it constant for the variations in workpiece thicknesses. The uniformity of the pressure is necessary not to offer an excessive resistance to the vertical movements of the feed dog but to make the independent biasing means sensitive in order to fully exploit the oscillation of the feed dog and maintain the sole ofthe presser-foot in contact with it so that the layers forming the work to be sewn by the machine will maintain alignment one with the other.

The area around the presser-foot has to be kept as clear as possible so as to provide necessary clearance for changeover to other attachments required by the machine. The independent biasing means must be disposed so that it is readily accessible and will not interfere with the normal working and maintenance of the machine.

The device must also be easily removable to provide for rapid assembly of other devices to the machine.

The aim of the present invention is that of making the assembly of the presser-foot simplified so that adjustment, when necessary does not involve any diffculty and at the same time provides for its easy removal from the machine.

To accomplish this feature, the problem solved was the construction of the independent biasing means and its location on the machine so that its point of application on the presser-foot does not cause interference with other supplementary devices.

A low-inertia presser-foot having independent biasing means is supported by a presser-foot bar from which and beneath which it protrudes and is operatively connected to the upper end of an oscillating support of the presser-t'oot and includes means for the selective adjustment of the pressure exerted by the biasing means on the said support.

The presserfoot bar is provided with an internal recess adapted to receive the independent biasing means and object of the invention is to provide an improved presserfoot device for a sewing machine of simplified construction, having a minimum of parts and which require a minimum amount of space to perform its intended function without interference with other attachments required by the machine.

A further and more specific object of the invention is to provide an improved presser-foot device for a sewing machine which can be quickly and easily attached to or detached from the machine without changing the settings of the presser-foot bar and the biasing means carried thereby to which the presser-foot is operatively connected.

Further aims and advantages of the present invention are those which are inherent and which will become apparent as the following detailed description of a preferred embodiment proceeds in reference to the figures of drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in side elevation and in partial section of a portion of a sewing machine showing the presserfoot device according to the invention applied thereto.

FIG. 2 is a sectional view of the device in FIG. 1 as seen looking in the direction of the indicating arrows of line IIII in FIG. I, and

FIG. 3 is a perspective view in exploded form showing the presserfoot device in greater detail.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 1 and 2., the presser-foot device generally indicated by numeral 10 includes a presser-foot bar 11 which is mounted for sliding movement in a supporting bushing 12 assembled in and which protrudes from the underside of that portion of a sewing machines frame identified in FIGS. 1 and 2 by numeral 13.

The presserfoot bar 11 carries on the lower end thereof a presserfoot l4 and on its upper portion the usual fabric pressing spring 15. One end of spring 15 engages an upper end 16 of the presser-foot bar and the other end is housed in an adjustment bushing 17 as shown in FIG. 2 on the upper portion of the frame 13 in vertical alignment with bushing 12. By simply turning bushing 17 in one direction or the other provides a means for increasing or decreasing the amount of pressure exerted by the fabric pressing spring 15 on the presser-foot bar 11. This bar 11 is connected to a conventional lifting device 18 which includes, among other parts, a collar 19 fixed on the upper end 16 of the said presser-foot bar and is connected by means of a screw 20 to a tie rod 21. The rod 21 is pivotally attached to the free end of a lifting arm 22 which is keyed on one end of a driving shaft 23 of the lifting device. The tie rod 21 is provided adjacent its lower end with an elongated hole 24 through which the screw 20 extends and permits vertical movement of the presser-foot bar 11 during normal operation of the machine within the limits of the elongated slot. The presser-foot bar 11 is normally urged downwardly by spring 15 so that the screw is located in the lower portion of the elongated hole 24 as shown in FIG. 1.

The presser-foot device 14 (FIG. 3) includes a support clamp 25 fixed on the presser-foot bar 11 by means of set screws 26. An oscillating support 27 of generally V-shape configuration of which one of the arms thereof is disposed above the other, and forms a pivoting head 28. The other arm is directed angularly downward and pivotally supports a sole plate 29 at its lower end (FIGS. 1 and 3).

Interposed between the sole plate 29 and the oscillating support 27 there is provided a coil spring 30 (FIG. 3) disposed so as to urge the free end of said sole plate 29 upwardly when the presser-foot is not in contact with the workpiece below it. The pivoting head 28 of the oscillating support 27 is pivotally attached to the clamp 25 intermediate a pair of spaced and integrally formed ears 31 depending therefrom by means ofa pin 32. The pivoting head 28 has on its rearward side a slot 33 into which assembles a roller 34 that is adapted to make contact with the independent biasing means 35 for continuously urging the oscillating support 27 and the sole 29 of the presser-foot device 10 in a downwardly direction (FIG. 2). The biasing means 35 is housed in a longitudinal recess 36 provided on the inside of the presser-foot bar 11 and includes a first pushrod 37 slidably mounted therein and which protrudes from the lower end of said bar. A helical spring 38 assembles on the first push rod 37 with one end in contact with a collar 39 fixed on the latter and the opposite end presses against a second push-rod 40 which is threadably assembled in the upper portion 16 of the said presser-foot bar 11. The first push-rod 37 is adapted to transmit the pressure exerted by the spring 38 to the oscillating support 27 with which said rod is operatively associated by means of the roller 34. The second pushrod is adjustable longitudinally to increase or decrease the pressure provided by a biasing means such as a coil spring 38 by simply turning said push-rod in one direction or the other. To provide for this adjustment, the second push-rod 40 includes an upwardly directed tang 41 which extends into an axially aligned bore 42 formed in the adjustment bushing 17 and is readily assessable through the top of said bushing with a screw driver or the like to turn said second push rod as desired. The independent biasing means 35 is housed by the presser-foot bar 11 to provide an improved compact device which will not create an interference in the area of the presser-foot where other auxilliary devices are normally mounted, such for example as the upper thread cutting device, the separation knife or the auxiliary work puller device.

A further advantage of confining the independent biasing means as described above is to keep the area above the frame 13 free of interference so that the bushing 17 can be easily adjusted.

Additionally, the arrangement of the elements comprising the independent biasing means permits the device to be quickly and easily removed from the machine as a unit.

During operation, high speed sewing machines have difficulty in maintaining reciprocal contact between the sole 29 of the presser-foot and the feed dog 43 when the latter is caused to move upwardly and to protrude through the needle plate 44. This condition can be attributed to the speed at which the feed dog 43 moves upwardly and thence parallel with the needle plate 44 during the performance of its intended function. The initial movement of the feed dog is an upwardly thrust, which movement is absorbed by the presser-foot device. Additionally when the feed dog 43 is caused to move rapidly downward the presser-foot device does not succeed in discharging, in the same rapid way, the energy stored in the fabric pressing spring during the lifting on to the presser-foot. For this reason the presser-foot is blocked during its downward movement, that is to say that the presser-foot bar does not descend as rapidly as the feed dog 43 so that only the pressure exerted by the independent biasing means 35 operates on the presser-foot to oppose the thrust of the feed dog.

The fabric pressing spring 15 is utilized, in this case, for the purpose of maintaining the presser-foot bar 11 in its desired location for combating those eventual greater thicknesses in the workpieces, such as cuffs or flaps, crossed seams, etc. which, because of their size, cause the support 27 to move upwardly while sewing the same. To control the limit of this movement, the clamp 25 is provided with an integral plate 45, which is angularly disposed and on which two stop screws 46 and 47 having lock nuts 48 are assembled. When tthe oscillating support 27 is pushed upwardly by an increase in thickness of a workpiece, the stop screw 46 contacts the roller 34 causing the forces of this upward movement to be absorbed by the fabric pressing spring 15. When the presser-foot is manually lifted and moved away from the needle plate 44 by means of the lifting device 18, tthe downward pivotal movement of the support 27 by the biasing means 35 is limited by an integrally formed lug 49 on said support which is disposed so as to contact the stop screw 47 and limit this movement.

The presser-foot bar includes a shoulder 50 (FIG. 2) which serves to retain the first push rod 37 within said presser-foot bar by causing collar 39 to seat on said shoulder when for any number of reasons the presserfoot 14 is removed from the machine. The pressure exerted by the spring 38 of the biasing means 35 is less than the pressure exerted by the fabric pressing spring 15; however, it is sufficient to perform the function of absorbing the thrust of the feed dog and to return the absorbed energy as the feed dog descends which is required to obtain the necessary forward movement of the layer of fabric forming the workpiece. With the support 27 being pivoted to the presser-foot bar, said support and the sole 29 are pushed upwardly by the feed dog to follow an arcuated path around the pin 32, as indicated by arrow A in FIG. 1. As the feed dog starts to descend near the end of the feeding cycle, the support 27 and the sole 29 move downwardly by the action of spring 38 and describes a path of travel opposite that indicated by arrow A in FIG. 1. This second movement provides a desired condition of maintaining contact between the sole 29 and the feed dog 43 and permits an increase in the speed of the forward movement of the workpiece which is directly in contact with said sole 29. Normally a condition exists where the upper layer of the workpiece has the tendency to be braked by the prcsser-foot due to the friction generated between the sole and said layer which does not provide a uniform forward movement of both layers. The presser-foot device of the present invention has corrected this condition for the arcuated path through which it travels during the performance of its intended function is effective in causing the presser-foot to serve as an upper puller during the lowering of the feed dog.

Although the present invention has been described in connection with a preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are consid ered to be within the purview and scope of the invention and the appended claims.

What is claimed is:

1. For a sewing machine of the type including a needle plate and a feed dog for advancing a workpiece as it is sewn, an improved low inertia presser-foot device comprising:

a. a presser-foot bar having an axial bore extending therethrough;

b. support means including 1. a clamp member attached to one end of said presser-foot bar.

2. an oscillatable support having a bifurcated pivoting head pivotably connected to said clamp member with said sole plate being pivotably attached to the other end of said oscillatable support, and

3. a roller member mounted between the bifurcations of said pivoting head;

c. independent biasing means carried by said pressure-foot bar and operatively connected to said roller member for urging the sole plate toward the feed dog; and

d. a fabric pressing spring with tension control means connected to said presser-foot bar for continuously urging the latter and the supporting means carried thereon under selected tension in a direction to effect contact of the sole plate with the workpiece as it is advanced by the feed dog.

2. The low inertia presser-foot device according to claim ll wherein said independent biasing means includes a spring biased first push rod housed in the axial bore of said presser-foot bar having one end thereof protruding from the lower end of the latter for operative contact with said roller member.

3. The low inertia presser-foot device according to claim 2 wherein said independent biasing means includes a second push rod having one end assembled for longitudinal adjustment within the axial bore of the upper end of said presser-foot bar for selectively changing the amount of force exerted by said spring biased first push rod on said roller member.

4. The low inertia presser-foot: device according to claim 3 wherein said presser-foot bar includes an internal shoulder for limiting the downward movement of said spring biased first push rod to prevent its removal from said presser-foot bar upon disassembly of said presser-foot device from the latter.

5. The low inertia resser-foot device according to claim 3 wherein said fabric pressing spring defines a coil spring assembled on said second push rod having one end in contact with said presser-foot bar and the other seated within a longitudinally adjustable bushing. k 1K 

1. For a sewing machine of the type including a needle plate and a feed dog for advancing a workpiece as it is sewn, an improved low inertia presser-foot device comprising: a. a presser-foot bar having an axial bore extending therethrough; b. support means including
 1. a clamp member attached to one end of said presser-foot bar.
 2. an oscillatable support having a bifurcated pivoting head pivotably connected to said clamp member with said sole plate being pivotably attached to the other end of said oscillatable support, and
 3. a roller member mounted between the bifurcations of said pivoting head; c. independent biasing means carried by said pressure-foot bar and operatively connected to said roller member for urging the sole plate toward the feed dog; and d. a fabric pressing spring with tension control means connected to said presser-foot bar for continuously urging the latter and the supporting means carried thereon under selected tension in a direction to effect contact of the sole plate with the workpiece as it is advanced by the feed dog.
 2. an oscillatable support having a bifurcated pivoting head pivotably connected to said clamp member with said sole plate being pivotably attached to the other end of said oscillatable support, and
 2. The low inertia presser-foot device according to claim 1 wherein said independent biasing means includes a spring biased first push rod housed in the axial bore of said presser-foot bar having one end thereof protruding from the lower end of the latter for operative contact with said roller member.
 3. The low inertia presser-foot device according to claim 2 wherein said independent biasing means includes a second push rod having one end assembled for longitudinal adjustment within the axial bore of the upper end of said presser-foot bar for selectively changing the amount of force exerted by said spring biased first push rod on said roller member.
 3. a roller member mounted between the bifurcations of said pivoting head; c. independent biasing means carried by said pressure-foot bar and operatively connected to said roller member for urging the sole plate toward the feed dog; and d. a fabric pressing spring with tension control means connected to said presser-foot bar for continuously urging the latter and the supporting means carried thereon under selected tension in a direction to effect contact of the sole plate with the workpiece as it is advanced by the feed dog.
 4. The low inertia presser-foot device according to claim 3 wherein said presser-foot bar includes an internal shoulder for limiting the downward movement of said spring biased first push rod to prevent its removal from said presser-foot bar upon disassembly of said presser-foot device from the latter.
 5. The low inertia presser-foot device according to claim 3 wherein said fabric pressing spring defines a coil spring assembled on said second push rod having one end in contact with said presser-foot bar and the other seated within a longitudinally adjustable bushing. 